This module defines a class which can serve as a base for parsing text
files formatted in the HyperText Mark-up Language (HTML). The class
is not directly concerned with I/O -- it must be provided with input
in string form via a method, and makes calls to methods of a
``formatter'' object in order to produce output. The
HTMLParser class is designed to be used as a base class for
other classes in order to add functionality, and allows most of its
methods to be extended or overridden. In turn, this class is derived
from and extends the SGMLParser class defined in module
sgmllib. The HTMLParser
implementation supports the HTML 2.0 language as described in
RFC 1866. Two implementations of formatter objects are provided in
the formatter module; refer to the
documentation for that module for information on the formatter
interface.

The following is a summary of the interface defined by
sgmllib.SGMLParser:

The interface to feed data to an instance is through the feed()
method, which takes a string argument. This can be called with as
little or as much text at a time as desired; "p.feed(a);
p.feed(b)" has the same effect as "p.feed(a+b)". When the data
contains complete HTML markup constructs, these are processed immediately;
incomplete constructs are saved in a buffer. To force processing of all
unprocessed data, call the close() method.

For example, to parse the entire contents of a file, use:

parser.feed(open('myfile.html').read())
parser.close()

The interface to define semantics for HTML tags is very simple: derive
a class and define methods called start_tag(),
end_tag(), or do_tag(). The parser will
call these at appropriate moments: start_tag or
do_tag() is called when an opening tag of the form
<tag ...> is encountered; end_tag() is called
when a closing tag of the form <tag> is encountered. If
an opening tag requires a corresponding closing tag, like <H1>
... </H1>, the class should define the start_tag()
method; if a tag requires no closing tag, like <P>, the class
should define the do_tag() method.

The module defines a parser class and an exception:

classHTMLParser(

formatter)

This is the basic HTML parser class. It supports all entity names
required by the XHTML 1.0 Recommendation (http://www.w3.org/TR/xhtml1).
It also defines handlers for all HTML 2.0 and many HTML 3.0 and 3.2 elements.

exceptionHTMLParseError

Exception raised by the HTMLParser class when it encounters an
error while parsing.
New in version 2.4.

Alternate HTML parser that offers a slightly
lower-level view of the input, but is
designed to work with XHTML, and does not
implement some of the SGML syntax not used in
``HTML as deployed'' and which isn't legal
for XHTML.